As a christmas present I bought myself some MCP23017's (among other things) but I can't get it working. I am new to i2c in general; so i am probably making a simple mistake. I have been following this tutorial over at tronixstuff

Here is a picture of my wiring; since this picture was taken I've added two pull up resistors (2.2o) from both SDA and SCL to the reset pin which is tied to 5v. As well I have ensured that the LED works.

hey there,try changing line Wire.write(11111111); to Wire.write(B11111111); or Wire.write(255); or Wire.write(0xff); i not a pro yet, but i think when u send binary you have to tell it somehow its birary. when i ve played with i2c stuff the most common problem is having the address wrong 0x20 looks right but u can try 0x40 too.i dont know if that helps,red